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I've got hypertension > Lecture 11 > Flashcards

Lecture 11 Flashcards

1
Q

The mesenteric veins and arteries drain from and supply the what?

A

intestines

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2
Q

What three things control blood flow?

A

myogenic control
neural control
metabolic requirements

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3
Q

Is regulation of blood flow uniform for all organs?

A

no

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4
Q

What are two examples of specialised regulation of blood flow?

A

coronary blood flow

pulmonary blood flow

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5
Q

Why is coronary blood flow important?

A

because the heart muscles are dependent on aerobic metabolism

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6
Q

The heart is dependent on what kind of respiration?

A

aerobic metabolism

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7
Q

How much of the cardiac output do the lungs receive?

A

100%

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8
Q

In the coronary circulation, where are large arteries and veins located? Where are smaller vessels located?

A

large ones are on the epicardial surface

smaller vessels penetrate into the myocardium

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9
Q

What percentage of the cardiac output does the heart receive?

A

5%

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10
Q

Where do the coronary arteries originate?

A

close to the aortic valve (the aortic root, where the aorta comes from)

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11
Q

What are the names of the two main coronary arteries and where do these go?

A

there is the left main coronary artery which feeds the left side of the heart, and the right main coronary artery which feeds the right side of the heart

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12
Q

What helps causes the perfusion of the coronary arteries?

A

When the heart is ejecting blood during systole, the aorta stretches. The elastic recoil of the aorta during diastole pumps the blood through the systemic circuit and into the coronary arteries

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13
Q

What does the right main coronary artery supply?

A

it supplies blood to the right atrium, right ventricle and inferoposterior region of the left ventricle (bottom part of the left ventricle)

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14
Q

What does the left main coronary split into?

A

the circumflex artery

the left anterior descending artery

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15
Q

What does the circumflex artery supply?

A

It branches to the back of the heart and supplies the left atrium and posterior left ventricle

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16
Q

What does the left anterior descending artery supply?

A

it supplies blood to the anterior side of the left ventricle

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17
Q

Every myocyte has lots of ________

A

capillaries

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18
Q

Why is it necessary that every myocyte had capillaries associated with it?

A

so that there can be lots of diffusion in a short distance and so there can be a constant supply of O2

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19
Q

Describe the drainage of blood in the coronary veins

A

The blood drains into the coronary veins and then into the coronary sinus and then they all empty back into the right atrium

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20
Q

At what stage of the cardiac cycle is the myocardium perfused?

A

during diastole

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21
Q

What happens to the myocardium perfusion during systole?

A

The myocardium contraction during systole means that the vessels are compressed. This means that there is a decrease in the radius of the blood vessels so increased resistance and decreased blood flow.

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22
Q

What happens to the myocardium perfusion during diastole?

A

The myocardium are relaxed and so the vessels are not compressed. This means that there is an increase in the radius of the blood vessels and so there is is decreased resistance and increased blood flow

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23
Q

Is the effect of diastole and systole on the perfusion of the myocardium more obvious in the right of left coronaries?

A

more severe in the left coronaries

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24
Q

Cardiac tissue has a

  • ________ metabolic rate
  • high ________ consumption
  • reliant on ________ metabolism
A

high
O2
oxidation

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25
Q

Is there high or low O2 extraction in the coronary circulation?

A

very high (65 - 75% from the blood)

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26
Q

What is the issue with there being a high O2 extraction from the coronary arteries?

A

When the metabolic demand, you can’t just extract more oxygen from the blood, you have to increase the flow to the heart

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27
Q

What happens to the blood flow to the heart when there is an increase in myocardial O2 demand like during exercise?

A

the supply of blood to the heart also increases

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28
Q

Explain the transient extrinsic control of coronary vessels and what is meant by the word transient

A

Sympathetic nervous system (which is active when we are exercising) released noradrenaline which binds to β1-adrenergic receptors which increase heart rate and stroke volume, and to the α1- adrenergic receptors which causes vasoconstriction. However, we need there to be an increase in blood flow because there is an increase in the metabolic demand so this doesn’t last long, hence it is transient
therefore the metabolic auto-regulation is an intrinsic factor of the vasculature

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29
Q

Why is the extrinsic control of the coronary heart flow considered transient?

A

Because the metabolic auto-regulation overrides the transient constriction from the activation of the sympathetic nervous system

30
Q

Describe the intrinsic metabolic auto-regulation that we can use to alter vascular diameter

A

If you increase your oxygen consumption, there is an increase in the metabolic biproducts which can stimulate vasodilation to increase blood flow to the heart

31
Q

If the metabolism goes up, you can produce ______

A

adenosine

32
Q

What is the effect of adenosine on coronary blood flow

A

Binding of adenosine to the receptors on the coronary vessels leads to vasodilation

33
Q

What are two another ways, apart from adenosine to increase blood flow in the coronary arteries?

A
  • NO is released from the endothelium, this relaxes the smooth muscle cells and causes vasodilation so there is decreases resistance and increased blood flow
  • hypoxia (low O2) can cause coronary vasodilation
34
Q

What can cause heart disease?

A

If there is problems with coronary blood flow

35
Q

What is an underlying cause of heart disease?

A

atherosclerosis

36
Q

What is atherosclerosis?

A

developments of lesions and plaque within the arteries that reduces the ability to deliver blood

37
Q

What are 4 preferential sites of formation of atherosclerosis?

A
  1. aortic sinus
  2. aortic arch
  3. brachiocephalic trunk
  4. carotid artery
38
Q

What can accelerate development of atherosclerosis?

A

high cholesterol and smoking

39
Q

If you get atherosclerosis in the coronary arteries, you can develop ________

A

angina

40
Q

What happens if the atherosclerosis blocks the artery?

A

you can have a heart attack

41
Q

atherosclerosis tends to occur in _________ arteries

A

large

42
Q

What is atherosclerosis lesion made of?

A

changes in smooth muscle cells, fat deposits, calcification

43
Q

How does atherosclerosis affect the supply and demand for O2?

Normally we have an increase in __________ which leads to an increase in coronary blood __________. In the diseased coronary arteries, this doesn’t work very well because the _______ mechanism doesn’t work and so the _______ doesn’t match the _______. _______ is not released so there is no vasodilation and so there is no _________ in ________ and there is decreased _________ capacity and you can get exercise induced _________

A

Normally we have an increase in demand which leads to an increase in coronary blood flow. In the diseased coronary arteries, this doesn’t work very well because the NO mechanism doesn’t work and so the demand doesn’t match the flow. NO is not released so there is no vasodilation and so there is no increase in flow and there is decreased vasodilator capacity and you can get exercise induced angina

44
Q

The pulmonary circulation is in _________ with the heart

A

series

45
Q

How much cardiac output does the pulmonary circuit receive?

A

100%

46
Q

The blood is ejected from the right ventricle and goes into the what?

A

pulmonary trunk

47
Q

What does the pulmonary trunk divide into?

A

the left and right pulmonary artery

48
Q

Is there a high or low surface area of circulation in the lungs? Why is this needed?

A

high

because that is where the gas exchange is going to occur - removal of CO2 and uptake of O2

49
Q

Once in the lungs, the circulation converts from a series circuit to what?

A

a range of different parallel circuits

50
Q

Do the lungs have high or low flow?

A

high

51
Q

Which is at a higher pressure, the pulmonary or systemic circulation?

A

the systemic

52
Q

If there is a high flow, low pressure in the lungs, what does this mean for the resistance?

A

it must be very low

53
Q

What is the pressure in the pulmonary circuit?

A

25/10 mmHg (instead of 120/80mmHg)

54
Q

How much less pressure is there in the pulmonary circuit compared to the systemic circuit?

A

it is 10-15x lower than in the systemic circuit

55
Q

How can we have such low resistance when we have such high flow in the lungs?

A

Because we have a large radius of the pulmonary trunk and arteries
and the length of the vessels are really small because the heart and the lungs are really close together so less resistance

56
Q

If there is an increase in CO, the pulmonary circulation has to deal with this. How does it do it? What is the advantage of this?

A

The vasculature is highly compliant, it distends easily and there is lots of elastin.
This means that the pulmonary pressure remains the same over a range of cardiac output

57
Q

Because they are highly compliant, pulmonary arteries behave more like what?

A

veins

58
Q

The decrease in pressure on the pulmonary circuit prevents what from occurring? Why is this necessary?

A

If prevents pulmonary capillary H2O loss. This is necessary so that there is no alveoli flooding which could affect our gas exchange

59
Q

How does posture affect the pulmonary circulation pressure?

A
  • if we are standing upright, the pulmonary pressure changes within the lungs: there is lower pressure in the upper regions of the lungs, higher pressure at the lower regions of the lungs
60
Q

In the upper regions of the lungs, we have reduced hydrostatic ________. Because the vessels are compliant, the vessels can start to partially ________, increasing the ________ (because you are decreasing the _______) and therefore you are going to reduce the _______ to the upper lobes of the lungs. This is called _______

A 
pressure
collapse
resistance
radius
blood flow
hypofusion
61
Q

In the lower regions of the lungs, we have __creased hydrostatic ________. Because the vessels are compliant, the vessels can start to ________, decreasing the ________ (because you are increasing the _______) and therefore you are going to increase the _______ to the lower lobes of the lungs. This is called __________

A 
in
pressure
dilate
resistance
radius
blood flow
hyperfusion
62
Q

Hypoperfusion at the upper lobes gives us the capacity to dilate and spread the blood flow around all of the lungs. When is this useful?

A

during exercise

63
Q

Describe the redundancy in the pulmonary vasculature circulation

A

We can recruit more vessels to distribute the cardiac output and blood flow throughout the lungs without changing the pressure

64
Q

What is hypoxia?

A

when there is not enough O2 that gets into the cells

65
Q

Most cells do what in response to hypoxia? How does this differ to the lungs?

A

normally the vascular beds vasodilate in response to hypoxia but in the lungs, they vasoconstrict

66
Q

Why is vasoconstriction in the lungs in response to hypoxia needed?

A

It is a way to divert blood away from poorly ventilate alveoli. If there is not fresh air going into the alveoli, there is no point sending the blood there for gas exchange

67
Q

What are two intrinsic controls of pulmonary blood flow and how do they work?

A
  • NO: this relaxes the smooth muscle and causes vasodilation to decrease resistance and increase blood flow
  • Endothelin-1: this contracts smooth muscle cells which leads to vasoconstriction, increased resistance and decreased blood flow
68
Q

What are two extrinsic control of pulmonary blood flow?

A
  • the α1-adrenoreceptor which stimulate vasoconstriction, increasing resistance and increasing pulmonary pressure
  • β2- adrenoreceptors which stimulate vasodilation which decreases resistance and pulmonary pressure
69
Q

How does the location of the α1-adrenoreceptors and β2- adrenoreceptors differ in the pulmonary circuit?

A

the α1-adrenoreceptors tend to be in the pulmonary trunk and left and right pulmonary artery whereas the β2- adrenoreceptors tend to be in the smaller resistance vessels

70
Q

The α1-adrenoreceptors and β2- adrenoreceptors just balance each other out. Why do we bother?

A

We need to adapt if things change eg. if you go high up on a mountain, you get generalised hypoxia and so there is less oxygen so in the pulmonary circulation, you get hypoxic vasoconstriction. But we don’t want this so there is activation of the sympathetic nervous system which stimulates the β2- adrenoreceptors in the small resistance vessels, leading to the vasodilation

I've got hypertension (47 decks)

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